The silicon based MEMS (Microelectromechanical System) microphones, also known as acoustic transducers, are playing a more and more important role in the hearing instrument, mobile communication system, digital camera, video camera and toy industry. Usually, a silicon based MEMS microphone chip needs to be packaged before it can be tested, shipped and utilized. U.S. Pat. No. 6,781,231 disclosed a typical MEMS package as shown in FIG. 1, which comprises surface mountable components 12 (e.g., a silicon based MEMS microphone chip, integrated circuits), substrate 14, and a cover 20, wherein the combination of the substrate 14 and the cover 20 forms a housing 22 in which the surface mountable components 12 are located and electrically connected.
However, there are several drawbacks to this MEMS package and its like. Firstly, it is not cost-effective. Packaging cost generally takes a major portion of the total cost for such a conventional packaged MEMS microphone, for example, for a typical 6 mm2 package size, the minimum packaging cost may exceed $0.1, whilst a typical MEMS microphone chip costs much less than $0.1. Especially, when package size is further reduced, which is a growing trend, packaging cost will become a cost-down bottle neck. Secondly, it is disadvantageous in manufacturability and mass production, since the singulated MEMS microphone chips needs to be packaged separately. Thirdly, performance consistency may not be guaranteed, particle and organic contaminations may not be easily prevented. Fourthly, size reduction of the MEMS package is highly limited due to its incompact structure.
To overcome the above drawbacks to the conventional packaged MEMS microphone, the present invention suggests a fully wafer-level-packaging technique for packaging a silicon based MEMS microphone. Actually, U.S. Pat. No. 8,368,153 discloses a wafer level package of MEMS microphone, as shown in FIG. 2, and manufacturing method thereof. However, the US patent application only discloses a chip structure of an MEMS microphone and a wafer process flow for manufacturing the same, the structure is actually not a packaged MEMS microphone which is surface mountable, and still requires traditional acoustic packaging after wafer process. Therefore, a fully wafer-level-packaged MEMS microphone, which is fully packaged at wafer level and does not need any further process after die singulation, and a method for manufacturing the same are still not applicable.